Claude Sonnet 4.6 vs Opus 4.6 in 2026: legacy status, context, pricing, and migration to Sonnet 5 and Opus 5

Claude Sonnet 4.6 and Claude Opus 4.6 are still active in the API but now officially legacy models. Anthropic recommends moving to Sonnet 5 and Opus 5 respectively.

The historical 4.6 comparison remains useful because both models established the 1M-context, 128K-output generation. In 2026, however, the migration economics have changed: Sonnet 5 is cheaper than Sonnet 4.6, while Opus 5 keeps Opus 4.6's base token price.

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SONNET 4.6 AND OPUS 4.6 ARE LEGACY, NOT RETIRED

Anthropic's current model pages mark both 4.6 models Active (legacy). Sonnet 4.6 has a retirement commitment no sooner than February 17, 2027, while Opus 4.6 remains active under Anthropic's published model lifecycle policy.

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Model	Status	Context / output	Price / MTok	Current replacement
Sonnet 4.6	Active legacy	1M / 128K	$3 / $15	Sonnet 5 at $2 / $10
Opus 4.6	Active legacy	1M / 128K	$5 / $25	Opus 5 at $5 / $25

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THE TWO 4.6 MODELS SHARE 1M CONTEXT AND 128K OUTPUT

Both models support text and image input, text output, adaptive thinking, a 1M-token context window, and 128K maximum output. Their original differentiation was capability and price rather than headline context capacity.

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SONNET 5 MAKES SONNET 4.6 HARDER TO JUSTIFY ON PRICE

Sonnet 5 costs $2 input and $10 output per million tokens versus Sonnet 4.6 at $3 and $15. That is a one-third reduction in both base input and output price while moving to the current Sonnet generation.

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OPUS 5 KEEPS OPUS 4.6'S BASE PRICE

Opus 5 is priced at the same $5 input and $25 output per million tokens as Opus 4.6. Anthropic positions Opus 5 as the stronger current Opus model, so migration does not require a base token-price increase.

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DS NORMALIZED WORKLOAD

For 10M input and 2M output tokens, Sonnet 4.6 costs about $60 at base rates, while Sonnet 5 costs about $40. Opus 4.6 and Opus 5 both cost about $100. Prompt caching and Batch API can change the effective cost materially.

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EXTENDED THINKING ALSO CHANGED

The 4.6 model pages now describe adaptive thinking as the current reasoning mechanism and mark extended thinking as deprecated for these models. Migration therefore affects both model generation and how reasoning effort is configured.

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WHEN KEEPING A 4.6 MODEL CAN STILL MAKE SENSE

A production system may temporarily keep 4.6 for regression stability, pinned evaluations, or controlled migration. New development should generally evaluate Sonnet 5 or Opus 5 first because Anthropic explicitly identifies them as the migration path.

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